The object of this work is the elucidation of the biochemical mechanism of compensatory skeletal muscle hypertrophy. These studies will give greater insight into the physiological regulation of normal and pathologic skeletal muscle metabolism and into the role of the nervous system in this regulation. Present topics of investigation include the relationship between stretch-induced hypertrophy and: 1) amino acid uptake and incorporation into muscle protein. 2) cellular content of contractile protein. 3) activity of the Na/K-dependent ATPase. 4) characterization of substances with stretch-like activity in this system.